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Old Sep 1, 2007 | 03:36 PM
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Talking cat questions

Was thinking about taking out my front cats or my rear cats but only 2 not all of them. Havent got up under there to look yet so i figured i would ask, are they welded in or are the just clamped? also is there any sensors in the front ones? If there is you think i could get a pipe from a exhaust shop already tapped for one? How much louder would it be with my setup? Im looking for more sound at idle with the out the back system its kinda quiet at idle but sounds great accelerating. So I am tryng to get the best of both worlds. If there is any one who has done this would you plz post a sound clip I would love to hear what it sounds like.

thanks,
 

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Old Sep 1, 2007 | 07:37 PM
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Also what about high flow cats? how much do yall think it would cost to get those installed and the other 4 taken out?
 
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Old Sep 2, 2007 | 09:23 AM
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Originally Posted by SUPERDUTY_untouchabl
Was thinking about taking out my front cats or my rear cats but only 2 not all of them. Havent got up under there to look yet so i figured i would ask, are they welded in or are the just clamped? also is there any sensors in the front ones? If there is you think i could get a pipe from a exhaust shop already tapped for one? How much louder would it be with my setup? Im looking for more sound at idle with the out the back system its kinda quiet at idle but sounds great accelerating. So I am tryng to get the best of both worlds. If there is any one who has done this would you plz post a sound clip I would love to hear what it sounds like.

thanks,
Haven't had any direct experience, but I think the big issue with removing the cats is dealing with the sensors that are built in to them. There are only two cats on my 06 and they are placed right off the exhaust headers. Can`t even really get a good look at them.
 
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Old Sep 2, 2007 | 09:32 AM
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you only have two? Maybe thy changed from 04 to 06.....
 
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Old Sep 2, 2007 | 09:49 AM
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Yep, they most certainly did and that is a good thing. I just added a Magnaflow muffler and my system could not really be called a cat-back because it begins a long ways after the cats. I'll try to post pics in the next couple of days.

BTW the 2004 HD that I just bought only has two cats as well, but I'm sure that my 04 Scab (the red one in my gallery) had 4.

Really not sure why 4 cats are required sometimes and only two other times. Seems to me they are just extra parts to screw up.
 
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Old Sep 2, 2007 | 01:32 PM
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I can't imagine you having 4 cats usually you just get 2 right up at the front of the truck sometimes right off the headers. I would say more than likely you have only 2 cats and 4 mufflers, I could see this being a lot more normal. I would think it would be to expensive for Ford to have 4 cats. I know my old 02 focus had one cat of the header and then two mufflers. I would say the ones farther back would be extra mufflers you should be able to tell by looking at them if they have sensor lines running to them their cats, other wise the mufflers. To get more or better sound I would suggest installing glass packs and see what you get. Most exhaust shops can advise so that you can get the sound you want.
 
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Old Sep 2, 2007 | 02:30 PM
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No I'm nearly positive I have 4 cats I think I even remember a post on here some were talking about it but i cant find it....... Ill keep doing reaserch I am probably going to call the exhaust shop tommorow and c how much high flow cats would set me back. If my parents would bring my truck back I would go look but for some reason they keep taking my truck instead of my dads.

P.S. ok nearly all the cat topics have been closed by wheelma1 (sorry if i missed spelled) I am not wanting to remove all the cats just thinking of a set of high flow's so plz dont lock this thread.
 

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Old Sep 2, 2007 | 10:18 PM
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What kind of gas mileage increase could I see with some high flow cats?
 
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Old Sep 2, 2007 | 11:24 PM
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I've been considering this ever since installing an aft-cat exhaust. I have an '04 and it has four cats, sucks. There are also four sensors, one after each cat. So the problem is that when you remove two cats you may change the emissions and cause the truck to modify its set up to fix a air/fuel ratio problem that is actually the result of having high flow cats instead. Thus far, I've yet to find someone who's actually done the operation and verified that it would work. It may require a programmer to manage the new exhaust mix. And the search for answers continues...

why is wheelma1 locking the threads, i've been researching this for months now..
 
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Old Sep 3, 2007 | 12:30 PM
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Originally Posted by champ7718
I've been considering this ever since installing an aft-cat exhaust. I have an '04 and it has four cats, sucks. There are also four sensors, one after each cat. So the problem is that when you remove two cats you may change the emissions and cause the truck to modify its set up to fix a air/fuel ratio problem that is actually the result of having high flow cats instead. Thus far, I've yet to find someone who's actually done the operation and verified that it would work. It may require a programmer to manage the new exhaust mix. And the search for answers continues...

why is wheelma1 locking the threads, i've been researching this for months now..
Rick, AKA wheelma1, is the moderator for the F150 forum and believe me he does not interfere with any thread until it has basically gone out of control. He has always been more than patient with fools, far more than I would ever have been.

Any good exhaust shop ought to be able to tell you the implications of what you propose. When I was getting my work done someone came in with what you proposed and the manager talked him out of it because of the sensor issues. I'm just very glad that both trucks I have now are two cat systems.
 
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Old Sep 3, 2007 | 02:38 PM
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What if you disconnect the battery like your suppose to do when you put a CAI on and make the computer relearn the air/fuel mix do you think that would work?
cuz I am willing to do just about anything to squeeze more gas mileage out of my truck.
 
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Old Sep 3, 2007 | 02:46 PM
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the first set of cat's are pre-cats and the second set are actual cats or something like that....it's kind of like mustang exhaust...i've heard of a bunch of people that take two off and have the rear sensors just welded into the exhaust tubing and everything works fine. you will hear a difference with that set up but you may lose some low end grunt...

at least thats what i think
 
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Old Sep 3, 2007 | 03:04 PM
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I think I read somewhere that you can get a $20,000 fine if you disable any factory emmissions controls, such as the pre-cats or otherwise.

I'd either replace all of them with high flow cats, or just leave it alone...
 
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Old Sep 3, 2007 | 03:26 PM
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There not that strict in arkansas. There is countless straight piped trucks around here. Although there has been rumors floatingaround that hey are trying to pass a law were you have to pass a emission test. Any ways back to the topic, From what I understand (Ive been reaserching for 3 days now) the front cats are pretty hard to get out and they are basicaly already a high flow cat. Its the back 2 that are so restrictive and you would think with them being so restrictive that if you put high flows on it that it would help gas mileage some.... I realy wish that some 1 that has put high flows on a 04 would chime in b/c I would realy hate the be the test dummy here.
 
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Old Sep 3, 2007 | 03:34 PM
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Originally Posted by SUPERDUTY_untouchabl
There not that strict in arkansas
It's a federal law...it's that strict everywhere...

I'd just recommend doing you homework and making sure it is capable of passing an emissions test.

Good luck!
 
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